Question

我在visual basic中编写代码。该程序的目标是获得一个函数，在调用时从数组中随机选择一个字符串。问题是，当按钮调用它时，它不会选择不同的值。我不知道为什么会这样做。还有谁知道如何在标签或文本中打印多行？这是我的代码。

Public Class lbl

Public Function Noun() As String
    Dim rand As New Random
    Dim index As Integer
    Dim nouns() As String = {"boy", "girl", "dog", "town", "car"}
    Dim sentence As String ' used to build a sentence

    index = rand.Next(5)
    sentence = nouns(index)
    Return sentence
End Function

Public Function outs(ByVal n1 As String) As String
    Dim result = n1
    Return result
End Function

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    lblRandom.Text = outs(Noun()) & outs(Noun())

    lblRandom1.Text = outs(Noun())

End Sub

Answer 1

Public Shared Function RandomNumber(ByVal lowerBound As Integer, ByVal upperBound As Integer) As Integer
    Return CInt(Math.Floor((upperBound - lowerBound + 1) * Rnd())) + lowerBound
End Function

Public Function Noun() As String
    Dim rand As New Random
    Dim index As Integer = -1
    Dim nouns() As String = {"boy", "girl", "dog", "town", "car"}
    Dim sentence As String ' used to build a sentence
    index = RandomNumber(0, 4)
    sentence = nouns(index)
    Return sentence
End Function

Public Function outs(ByVal n1 As String) As String
    Dim result = n1
    Return result
End Function

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click

    lblRandom.Text = outs(Noun()) & outs(Noun())

    lblRandom1.Text = outs(Noun())

End Sub

Answer 2

问题是每次调用Noun（）函数时都会重新创建一个新的随机生成器。随机数生成器应该是一个全局变量。

Answer 3

问题是.NET随机数生成器根据种子生成随机数。种子是基于当前系统日期和时间的整数。如果您快速连续多次调用随机数生成器，则可能会使用相同的种子并生成相同的“随机”数字。解决方案是在您希望生成随机数的过程之外声明Random对象，并将种子传递给从当前（随机）日期和时间构建的构造函数。

回答您的其他问题。如果文本包含回车符，则标签控件将自动换行文本。我在下面为lblRandom添加了一个回车。

要在文本框中包装文本，请将其Multiline属性设置为True。

@Aly El-Haddad发布的代码也可以使用，但它包含一些VB6遗留代码。我试图尽可能保持.NET。我还消除了多余的“出局”程序并使其灵活，以便您可以在“名词”数组中添加或删除元素。请注意，使用“index = rand.Next（5）”行，您将包含不存在的数组的元素5。从零开始的数组的上限为4，因此当随机数生成器返回5时，将抛出“索引超出数组范围”错误。

 Private myRandom As New Random(CType(DateTime.Now.Ticks Mod Int32.MaxValue, Integer))

 Private Function Noun() As String
     Dim index As Integer
     Dim nouns() As String = {"boy", "girl", "dog", "town", "car"}
     index = myRandom.Next(nouns.GetLowerBound(0), nouns.GetUpperBound(0))
     Return nouns(index)
 End Function

Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
     lblRandom.Text = Noun() & Constants.vbNewLine & Noun()
     lblRandom1.Text = Noun()
End Sub

调用3次时，该函数似乎没有改变值

3 个答案: